Method of recovering metals from alloys.



UNITED STATES PATENT OFFTQE.

JULIUS H. GILLIS, OF TORONTO, ONTARIO CANADA, ASSIGNOR TO BRITISHAMERICA NICKEL CORPORATION LIMITED, OF TORONTO, ONTARIO, CANADA, ACORPORATION Patented Mar. 26, 1918.

OF CANADA.

METHOD OF RECOVERING METALS FROM ALLOYS.

1,260,661. Specification of Letters Patent.

No Drawing.

To all whom it may concern:

Be it known that I, JULIUS HOWELLS GIL- LIS, a citizen of the UnitedStates, residing at Toronto, Province of Ontario, Canada, have inventedcertain new and useful Improvements in the Methods of Recovering Metalsfrom Alloys, of which the following is a specification.

This invention is an electrolytic method whereby a metal may berecovered in a state of substantial or commercial purity from itsalloys. The invention will be described by reference to a specificillustrative example thereof, according to which nickel is deposited atthe cathode, a nickel-copper anode being employed: but the novelprinciple thereby illustrated is applicable to the electrolytic recoveryof other metals from their alloys.

Nickel-copper alloys wherein nickel predominates are readily obtainableby smelting the appropriate ores. As an illustration of this invention,I cast into any convenient anode form an alloy containing for exampleabout two parts of nickel by weight for each part of copper. This anodeis suspended in a suitable electrolyte, for example a weak solution ofnickel sulfate, together with a cathode of sheet nickel, iron or otherappropriate material. If now the electric current be caused to flow fromthe anode to the cathode through the electrolyte, as under the usualconditions for electro-depositing metals, it will be observed that for ashort period of time the cathode deposit will consist of pure nickel.During this same period both nickel and copper will pass into solutionat the anode, the nickel in predominating proportion. This is due inpart to the fact that nickel predominates in the composition of theanode, and in part to what ma for convenience be termed the selective effeet of the current, under the influence of which nickel tends todissolve more rapidly than copper. If the electrolysis be continuedunder these conditions, copper will begin to separate at the cathode.

If, however, the polarity of the electrodes be reversed, or the currentbe caused to flow to the alloy electrode as cathode, the socalledselective effect of the current is again displayed, and the copper isre-deposited at the alloy electrode, while at the same time aApplication filed September 4, 1917. Serial No. 189,601.

certain quantity of the deposited nickel is re-dissolved from theelectrode which originally functioned as the cathode. The amount ofnickel thus dissolved is nearly equivalent to the quantity of copperre-deposited, but represents only a fraction of the total nickel whichwas electrodeposited before the reversal of the polarity. There istherefore a certain net gain of nickel deposited upon the cathodeyandinasmuch as the copper ions have been driven from solution, theelectrolyte is restored to its original purity. The copper isre-deposited in loose or non-adherent form upon the alloy elecmode, thisslime or mud falling to the bottom of the cell and leaving the anode ingood condition for further dissolution when the original polarity isrestored. Therefore I am enabled, by reversing the current at properintervals and for proper periods, to recover the nickel in the form of areguline cathode deposit, while obtaining the copper as an anode slime.Although as above stated the operation may be so conducted as to afforda substantially pure cathode deposit of nickel, an absolute separationas between nickel and copper is not essential to the practice of myinvention. I have found it desirable in practice to reverse the currentat very short intervals,

so that time is not afforded the copper ions to wander too far from thealloy electrode. For example, ten reversals of the current per minute,each reversal having a duration of approximately two seconds, has beenfound in practice to give satisfactory results with an alloy anode ofthe characterabove mentioned; although it will be understood that myinvention is not limited to these specific conditions.

The duration of the current flow to the alloy electrode functioning ascathode, or in other words, the duration of the reversed flow, is soregulated as to suffice only for the re-deposition of the copper whichhas been dissolved: but it will be clear that this regulation may beaccomplished either by using the reversed-current (flowing to the alloyelectrode as cathode) for a reduced period as compared with the directflow; or, alternatively, by maintaining the same or even longer timeintervals during the reversal, and correspondingly reducing the currentflow (amperage), as for example by reversing the current through arheostat or other suitable resistance, or the like.

I have also found that the copper-bearing anode slimes contain certainimpurities, such as iron, the separation of which from nickel inelectrolytic processes has heretofore presented serious difliculties.

I also find it to be an advantage to separate the electrodes by a porousdiaphragm, which prevents the impure slimes from crossing over and beingdeposited on the cathode without electrolytic action, but I do notintend that my invention shall be limited in this respect.

If instead of reversing the current the latter be merely interrupted,the interruptions being sufficiently prolonged, a somewhat similaretfect as to precipitation of copper is secured, owing to local currentsset up within the cell. This actlon, however, is relatively very slow,and it is therefore preferred to impress current from an outside sourceupon the cell during the period of reversed flow. Nevertheless, I regardit as within my invention to interrupt the current for the time and atthe intervals necessary to accomplish the results herein abovedescribed.

I claim 1. The method of recovering metals from alloys thereof, whichconsists in passing an electric current from an alloy electrode to asuitable cathode through an electrolye containing a salt of a metal tobe deposited; and reversing the polarity of the electrodes at suchintervals and for such periods as to avoid substantial deposition uponthe cathode of any undesired components of the alloy anode.

2. The method of recovering nickel from nickel-copper alloys, whichconsists in passing an electric current from a nickel-copper anode to asuitable cathode through an electrolyte containing a s It of nickel; andreversing the polarity ofthe electrodes at such intervals and forsuchperiods as to avoid substantial deposition of copper upon thecathode.

In testimony whereof, I aflix my signature.

JULIUS H. GILLIS.

